package com.xiaotu.singleton.type4;

/**
 * @author 张晓
 * @create 2020-06-18 16:21
 */
public class SingletonTest04 {
    public static void main(String[] args) {
        //测试
        System.out.println("懒汉式2，线程安全");
        Singleton instance = Singleton.getInstance();
        Singleton instance2 = Singleton.getInstance();
        System.out.println(instance == instance2);

        System.out.println("instance.hashCode()=" + instance.hashCode());
        System.out.println("instance2.hashCode()=" + instance2.hashCode());
    }
}

//懒汉式（线程安全，同步方法）
class Singleton {

    private static Singleton instance;

    private Singleton(){};

    //提供一个静态的公有的方法，加入同步处理的代码，解决线程安全问题
    //既懒汉式
    public static synchronized Singleton getInstance(){
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }

}
